The present invention is related to semiconductor devices, and, in particular, is related to a data amplifying circuit that senses and amplifies a voltage difference between input signals and an output driver including the same.
Semiconductor devices such as memories usually contain data amplifying circuits. Such data amplifying circuits enable data to be valid to internal circuits, external circuits, or other circuit elements for the semiconductor devices.
On the other hand, data signals provided to other circuit elements or the external circuits have various swing levels required in accordance with operation modes. In a normal mode, a data amplifying circuit that generates an output signal quickly responding to an input signal even with a smaller swing level is needed. But, a test mode is required of an output signal oscillating in a larger swing level even with slowly responding to an input signal. For instance, in a direct access mode that directly accesses a memory cell array and verifies data values stored therein, an output signal from a data amplifying circuit is required to have a large swing level.
FIG. 1 is a circuit diagram of a conventional data amplifying circuit 10. In the data amplifying circuit 10 of FIG. 1, NMOS transistors 11 and 13 sense and amplify a voltage difference between first and second input signals VIN1 and VIN2. First and second output signals VOUT1 and VOUT1 are regulated in their swing levels by resistors R11 and R12 and a current source 15. Usually, the swing levels of the output signals from the data amplifying circuit 10 shown in FIG. 1 are established in the range of 200-300 mV on the basis of an operation of the normal mode. Otherwise, in the test mode such as the direct access mode, the output signal needs to have its swing level over 600 mV in order to provide valid data reception for the test equipment.
However, in the data amplifying circuit 10 shown in FIG. 1, a source current flowing into a source node NS0 is restricted by the current source 15. Therefore, it is difficult to provide the output signals of the data amplifying circuit 10 for test equipment with valid conditions during the test mode. There has been used an approach to increase the values of the resistors R11 and R12 in order to enlarge the output swing level. However, that approach also presents a burden in adjusting the values of the embedded resistors R11 and R12, resulting in lost time and increased cost.